The present invention relates to a machining arrangement and, more particularly, to a surfacing or finishing machine which includes a surface grinder, a cylindrical grinder or the like by which high precision machining of a workpiece is obtained by a grinding wheel or edging tool.
In machining operations, it is generally necessary to machine the surface of a workpiece to a mirror-like finish. To accomplish such finishing, it is absolutely required that the machining be effected by a rotating tool such as a grinding wheel or an edged tool with vibrations at the rotating tool being maintained at an absolute minimum.
In conventional surfacing or finishing machines, the drive motor for rotating the wheel spindle which is a working spindle or a pulley for transmitting mode of power are sources of vibrations which are transmitted to the surfacing tool or spindle slider for supporting the wheel spindle. This transmission of vibrations adversely affects the finishing of the surface of the workpiece and, by virtue of the construction of conventional machines, it is impossible to rotate the wheel spindle without generating and transmitting vibrations to the surfacing tool as will become more apparent from the following description of a conventional grinding machine.
In a conventional finishing or surfacing machine such as, for example, illustrated in FIG. 1, a machining tool such as a grinding wheel 101 is fixed to a wheel spindle 102 at one end portion with a pulley 103 being fixed to the other end portion of the wheel spindle 102.
The wheel spindle 102 is supported by bearings 105 installed within a bearing housing 104 fixed to a spindle slider 106 which is slidably guided by a column 108 arranged on a machine bed 107. A saddle 109 and a machine table 110 are disposed on the machine bed 107 and are movable in a vertical direction against the movement of the bearing housing 104 with the workpiece 111 being mounted on the table 110 so as to permit machining by the grinding wheel 101.
A motor 112 for rotating the grinding wheel is fixed on a floor 126 through a rubber damper 113 or on the machine bed 107 with the driving power from the motor 112 being transmitted from a motor pulley 114 to a belt 115 which rotates a pulley 116 around a first shaft 117 fixed to the machine bed 107. A second shaft 118, having rotatably mounted thereon a pulley 119, is fixed to the spindle slider 106 with driving power being transmitted between the pulley 119 and spindle pulley 103 by a belt 120. A first pair of arms 121 are rotatably mounted at one end thereof on a fixed shaft 117 with the other ends thereof being mounted on a movable shaft 122 having a pulley 123 rotatably mounted thereon. A second pair of spaced arms 121' are arranged between the movable shaft 122 and the fixed shaft 118 with first ends of the arms being rotatably mounted on the shaft 118 and the other ends thereof rotatably mounted on the movable shaft 122. A belt 124 is arranged between the pulley 116 and the pulley 123 and another belt 125 is arranged between the pulley 123 and pulley 119, whereby the drive power from the motor 112 is transmitted to the wheel spindle 102 through the respective belts and pulleys. While the afore-described conventional surface grinder attempts to minimize the undesirable vibrations generated by the motor from being transmitted to the wheel spindle, we have found that the vibrations may be transmitted to the wheel spindle from other unexpected portions of the drive arrangement of the surface grinder. Specifically, we have determined that the first pulley transmitting the driving power from the first belt to the second belt, in the course of its rotation around the first fixed shaft, generates rotating vibrations which are transmitted from the first fixed shaft to the machine bed by virtue of the fact that the shaft is fixed thereto. The vibrations generated by the rotating first pulley are transmitted to the wheel spindle through the column and spindle slider. Additionally, during rotation of the pulley around the second fixed shaft, further vibrations are generated and transmitted by the second fixed shaft to the wheel spindle through the spindle slider.
Consequently, in practical operation, one disadvantage of the afore-described conventional surface grinder resides in the fact that, due to the fixed connection to the machine bed and spindle slider, portions of the link mechanism which provide the required tensional force to the transmitting belts generate and transmit vibrations to the wheel spindle so that high precision machining of a workpiece is not possible.